And while Cooper, Helms, Galifianakis and Ken Jeong (reprising his role from the first film) serve up terrific performances and plenty of humor, "Hangover Part II" is so similar to its predecessor -- right down to the "hurry up and get to the wedding" climax -- that the story feels stale after about the first 30 minutes. Director Todd Phillips and his filmmaking team could have taken a lesson from anyone who has ever experienced an actual hangover: One is enough.

Phil (Cooper), Stu (Helms), Doug (Justin Bartha) and Alan (Galifianakis) -- the "wolf pack" from the first flick -- reunite for Stu's wedding to Thai beauty Lauren (Jamie Chung of "Sucker Punch"). Stu is somewhat of a square, ridiculed by his condescending soon-to-be father-in-law and determined to avoid the same kind of bachelor-party antics that led him to lose a tooth in the first "Hangover." So the gang -- joined by Lauren's younger brother Teddy (Mason Lee) -- agrees to a quiet night on the beach (with only a six-pack of beer) in lieu of a traditional bachelor party.

If only it were that easy. Phil, Stu and Alan awake in a dingy room with no memory of the previous night. Alan's head is mysteriously shaved and Stu has a tribal tattoo on the left side of his face. Doug and Teddy are nowhere in sight, though a phone call from Doug reveals that he left the group earlier in the night. As Stu and company go into full-blown panic mode searching for Teddy, they turn to help from gangster Mr. Chow (Jeong) and a pint-sized monkey that sports a tiny Rolling Stones jacket.

Chaos reigns as the gang hunts for Teddy, leading to interactions with a no-nonsense tattoo artist (a cameo by "Alpha Dog" director Nick Cassavetes), a pair of Russian drug dealers, a wheelchair-bound monk and a group of transsexual Thai prostitutes. "I can't believe this is happening again!" Stu exclaims. Well, neither can the viewers.

"Hangover Part II" is not a stand-alone film, so if you haven't seen the first one, don't bother with the second. Characters and scenarios from the gang's wild experiences in Las Vegas are frequently recounted, including even a return cameo by former boxing champ Mike Tyson. Laugh-out-loud moments abound early on, usually courtesy of Galifianakis and Cooper, but taper off down the stretch. A pre-Thailand scene in Alan's bedroom, where a poster of recently deceased pro wrestler Randy "Macho Man" Savage hangs on the wall like a specter, is rife with humor.

But the novelty of the first "Hangover" has worn off, and a lack of creativity (not to mention an uptick in squirm-inducing debauchery) makes the film feel like the cinematic equivalent of the backwash at the bottom of a beer bottle. The monkey is an amalgam of the baby and the tiger from the first "Hangover"; the guys have to get to Stu's wedding instead of Doug's; the tattoo artist stands in for the doctor from the first flick; and so on.

Although Cooper, Helms and Galifianakis give it a yeomen's effort and truly do shine in their respective roles, the seen-it-all-before factor lands "Hangover Part II" directly in the drunk tank.